The Clinical Impact of Solid and Micropapillary Patterns in Resected Lung Adenocarcinoma

Abstract Introduction Since the new adenocarcinoma (ADC) classification was presented in 2011, several authors have reported that patients with solid (S) and/or micropapillary (MP) predominant patterns showed a worse prognosis. On the other hand, there are several patients who have S and/or MP patterns even if their patterns are not predominant. However, the evaluation of these patients is uncertain. Methods A total of 531 ADCs were examined. We classified the patients into five subgroups according to the proportion of S and/or MP patterns: (1) both patterns absent (S–/MP–), (2) S predominant (S pre), (3) MP predominant (MP pre), (4) S pattern present although not predominant and MP pattern absent (S+ not pre/MP–), and (5) MP pattern present although not predominant (MP+ not pre). Results Of the 531 ADCs, 384 (72.3%) were classified as S–/MP–, 55 (10.4%) as S pre, 11 (2.1%) as MP pre, 42 (7.9%) as S+ not pre/MP–, and 39 (7.3%) as MP+ not pre. In a univariate analysis, the recurrence-free survival (RFS) and overall survival differed significantly among the five subgroups ( p p Conclusion Patients with S and/or MP patterns have a poorer prognosis even if their patterns are not predominant. The S and/or MP patterns must be treated at the time of diagnosis.